Rosacea is a chronic and gradual common inflammatory dermatosis related to vascular disorders. It mainly affects the central portion of the face and is characterized by reddening of the face accompanied by hot flushes, facial erythema, papules, pustules, telangiectasias and sometimes ocular lesions called ocular rosacea. In extreme cases, especially in humans, hypertrophy is observed at the nasal level called rhinophyma. Rosacea evolves over several years with outbreaks worsened by various stimuli like temperature variations, alcohol, spices, solar exposure or emotions.
Rosacea is classified into four subtypes depending on various clinical characteristics (Wilkin J et al., JAAD, 2002, 46: 584-587).
Subtype 1: also called erythematotelangiectasic rosacea, mainly characterized by flushes and a persisting central facial erythema. The presence of telangiectasias is common, but not essential to the diagnostic of this subtype. A central facial oedema, burning and stinging sensations and roughness or desquamation are also sometimes observed. The patients have erythrosis outbreaks due to sudden dilation of the arterioles of the face which then assume a congestive, red aspect. These outbreaks are caused by emotions, meals, temperature variations and are designated by the term of flushes.
Subtype 2: Also called papulopustular rosacea, which is characterized by an inflammatory stage with occurrence of inflammatory papules and pustules but without attaining the sebaceous follicle and therefore with absence of cysts and comedos. Papulopustular rosacea is characterized by persistent central facial erythema and by transient papules and/or pustules distributed at the centre of the face. However, the papules and pustules may also affect peri-orificial regions (i.e. peribuccal, perinasal or periocular areas). The papulopustular subtype recalls ordinary acne, but the comedos are absent. Rosacea and acne may coexist and, in addition to the papules and pustules suggesting rosacea, the concerned patients will also possibly have comedos. Patients affected by papulopustular rosacea will sometimes complain of burning and stinging sensations.
Subtype 3: Called Phymatous Rosacea (Rhinophyma)
Phymatous rosacea shows signs of thickening of the skin, nodules with an irregular surface and swelling. Rhinophyma is the most common presentation but phymatous rosacea may affect other territories, including the chin, the forehead, the cheeks and the ears. In patients affected by this subtype, the presence of enlarged and prominent follicular apertures is sometimes reported in the affected region, as well as telangiectasias. This belated phase essentially affects men. The patients have a red voluminous nose, covered with bumps with sebaceous hyperplasia and fiber reorganization of the conjunctive tissue.
Subtype 4: Called ocular rosacea (or ophthalmic rosacea). Ocular rosacea is often poorly diagnosed or underestimated as a cause of conjunctival inflammation. The diagnosis of ocular rosacea should be contemplated when a patient has one or several of the following signs and ocular symptoms: watery or blood-injected aspect (interpalpebral conjunctival hyperemia), foreign body, burning or stinging sensation, dryness, itching, photosensitivity, blurred vision, telangiectasias of the conjunctiva and of the edge of the eyelid or erythema of the eyelid and periocular erythema. Blepharitis, conjunctivitis and irregularity of the edges of the eyelid are other possibly detected signs. A chalazion or a chronic staphylococcus infection, apparent as a sty, and the cause of which is a dysfunction of meibomian glands, is a frequent sign of ocular affection related to rosacea. Certain patients will complain of decreased visual acuity, which is due to corneal complications (punctated keratitis, corneal infiltrates/ulcerations of the cornea or marginal keratitis).
Flushing histories are common in patients affected with erythematotelangiectasic rosacea (subtype 1) and sometimes also in those affected with papulopustular rosacea (subtype 2).
Flushing is a congestive or vasomotor outbreak, a phenomenon which is expressed by the appearance of transient red spots mainly at the face and accompanied with a sensation of heat. This symptom is common to several pathologies including rosacea.
Flushing may be triggered by various stimuli of daily life: Fast change of temperature, food, alcoholic beverages.
Its unexpected and elusive nature makes it difficult to study.
Presently in clinical trials, the assessment of the efficiency of candidate drugs is carried out via a questionnaire given to the patient who records in his/her daily life, the occurrence of this symptom and attempts to characterize it.
Certain methods have been proposed for measuring flushing. For example, Wilkin (J Invest Dermatol, 1981, 76, 15-18) propose the use of a thermal circulation index. This index is the ratio of the effective heat conductivity of cutaneous tissues relatively to the effective heat conductivity of the environment. In order to measure flushing, this author proposes the measurement of malar skin and the measurement of the malar thermal circulation index. These parameters are measured before the stimulus and upon maximum change in the malar temperature. Next, the ratio between both of these measurements is studied. Moreover, the time between the application of the stimulus and the moment corresponding to half of the maximum change in malar temperature was measured. However, these methods do not give the possibility of differentiating a pathological flush (notably of a subject suffering from rosacea) from a normal flush (healthy subject).
Thus, there still exists a great need for a stricter and reproducible method for measuring congestive outbreaks, notably those related to rosacea, and to thereby assess the impact of candidate drugs on this symptom. Notably, there exists a need for a method not coming under or not uniquely from the appreciation of the patient and giving the possibility of obtaining statistically significant results with a group of patients as small as possible.